And type reed switch control



April 1, 1967 H. MATTHIAS 3,

"AND" TYPE REED SWITCH CONTROL Original Filed Jan. 5, 1963 2 Sheets-Sheet l NI COIL l5 NI COIL l2 INVENTOR LYNN H. MATTHIAS BY WWW ATTORNEY April 1967 L. H. MATTHIAS 3,314,029

"AND' TYPE REED SWITCH CONTROL Original Filed Jan. 5, 1965 2 heetsh et 2 INVENTOR LYNN H. MATTHIAS Maw ATTORNEY United States Patent 3,314,029 AND TYPE REED SWITCH CONTROL Lynn H. Matthias, Fox Point, Wis., assignor to Allen- Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Original application Jan. 3, 1963, Ser. No. 249,185, now

Patent No. 3,215,795, dated Nov. 2, 1965. Divided and this application July 6, 1965, Ser. No. 469,593

3 Claims. (Cl. 335-451) This application is a division of application Ser. No. 249,185 filed Jan. 3, 1963 for Reed Switch Control, now Patent No. 3,215,795 dated Nov. 2, 1965. The invention relates to reed switch controls and it more specifically resides in a reed switch having two magnetic reeds with relatively movable contact ends, a magnetic member disposed adjacent the contact ends to modify magnetic field patterns associated with the reeds, and operating coils located on both sides of the magnetic member which function to close the reed contacts when both coils are energized.

Reed switches comprise a pair of thin, magnetic reeds within a glass envelope. At least one of the reeds is deflectable, and the ends of the reeds overlap slightly to function as switch contacts that move between open and closed positions in response to associated operating coils or other energizing means. These switches are particularly useful in circuits utilizing numerous switching elements that must operate with a very high degree of reliability over an extended time, and they are characterized by a rapid switching operation that makes them ideal for computer devices, logic circuits and telephone circuits.

In a host of reed switch applications the switch is combined with a pair of operating coils, and the reed contacts are to close only when simultaneous independent signals are transmitted to such associated coils. Crosspoint switching is a typical application of this nature. In some other applications the reed switch must also return its contacts to open position upon discontinuance of either of the signals. element for both energization and deenergization of the operating coils.

In ususal construction employing a pair of operating coils, each coil encircles one of the reeds and when it is energized by a current of prescribed value it developsa magnetic flux insufficient to close the switch. However, upon energization of both coils the resultant flux in the vicinity of the reed contact ends closes the switch, and in the instance of and type switch deenergization of a single coil will cause the switch to reopen. Such a devicemay have limited magnetic tolerances for proper operation, with the result that either excessive or deficient amounts of flux may be developed it any construction or operating parameter is altered to any considerable degree. For example, when the magnetizing force of each individu'al' coil is small enough to be below the drop out (switch opening) value, the combined magnetizing forces obtained upon simultaneous energization of the coils may not be much greater than the minimum at which switch closing will occur. In such switches a decrease in the applied voltages may result in the switch not closing when both coils are energized, and also the switch may remain closed when one coil is de-energized if the operating voltage is slightly increased. Also, if there is a small diiference between the magnetizing force required to pick up the switch and the magnetizing force required to drop out the switch, then a relatively small increase in voltage applied to a single coil may cause switch closure. Thus, some reed switch controls have serious disadvantages.

The present invention comprises a control for a reed switch having a main operating coil for each reed in combination with a magnetic member disposed in the im- It then functions as an and logic circuit ice mediate vicinity of the reed contact ends at a position between the coils. This magnetic member modifies the magnetic field in the vicinity of the contact ends to insure retention of the reeds in their initial open position upon energization of only one of the main operating coils. This retention is maintained for large values of magnetizing ampere turns being applied through the single coil, so that applied voltages can increase without affecting the characteristic of retaining the switch open until signals are applied to both coils.- Thus, only upon energization of both coils will the reed contacts be actuated to closed position. The presence of the magnetic member also improves switch opening characteristics in'that the applied voltage to the coils does not have to be as critically controlled in order to have switch opening occur when one coil is deenergized. To further enhance a rapid, positive reopening of the reed contacts a supplementary reverse coil is used with each main coil to reduce the magnetic potential between the reed contacts upon deenergization 'of either main coil. Then, extreme reliability is obtained for operation as an and logic circuit element.

It is an object of this invention to provide a reed switch control which will operate over a large range of line voltages without impairing the operating characteristics of the switch assembly.

It is another object of this invention to provide a reed switch assembly in which magnetic interaction between closely adjacent switches is reduced to levels wherein adjacent switches do not influence one another, so that a compact assembly of a plurality of reed switches may be obtained.

It is another object of this invention to provide a reed switch control which is characterized by reliable operation, and which is not handicapped by severely critical switch response characteristics.

It is another object of this invention to provide a reed switch control that may be readily manufactured in large numbers with substantial manufacturing tolerances.

The foregoing and other objects and advantages of this invention will appear from the description to follow. In the description reference is made to the accompanying drawings which form a part hereof, and in which there are shown by way of illustration, and not of limitation, specific embodiments of reed switch controls. For a determination of the scope ofthe invention, as distinguished from the specificness of the embodiments illustrated, referonce is made to the claims appended hereto.

In the drawings:

FIG. 1 is a view of a reed switch control with a magnetic flux diverting plate broken away and in section and with operating coils depicted schematically,

FIG. 2 is a graph of characteristics of the reed switch of FIG. 1,

FIG. 3 is a view of a reed switch control embodying the invention, and

FIG. 4 is a side view, with parts in section, of an assembly of a number of reed switch controls of the invention.

Referring now to the drawings, there is shown in FIG. I a sealed, glass envelope 1 preferably filled with an inert gas. A pair of long, thin reeds 2 and 3 extend into I the interior of the envelope 1 from its opposite ends 4 and :5. The reeds 2, 3 are of a magnetic material that has suificient flexure to provide for movement of the inner ends 6, 7 at the center of the envelope 1. The inner ends 6, 7 are normally open and they overlap slightly to present facing contact surfaces that will move into engagement with one another in response to magnetic forces established by associated coils. The reeds 2 and 3 also have sufficient conducting qualities to form satisfactory switch elements for an electric circuit, and thin external ends 8 and 9 function as terminals for connection high speed switching is essential.

The glass envelope 1 extends through a close fitting opening of a magnetic plate 11 that is centered with respect to the contact ends 6 and 7. A first operating coil 12 encircles the left hand end of the envelope 1, as viewed in FIG. 1, and its ends are joined to a pair of terminals 13 and 14. A second operating coil encircles the right hand end of the envelope 1 and has one end joined to the common terminal 13 while its other end extends to a terminal 16. Thus, thetwo coils 12, 15 can be independently energized, and if desired they can have entirely separate terminals instead of a common connection such as at the terminal 13.

In the operation of the device of FIG. 1, the presence of the magnetic plate 11 provides a mode of operation distinctly different from that heretofore had in the absence of such member. If either coil 12 or 15 is energized, without any energization of the other, the contact ends 6, 7 will remain open, and this open condition will persist for large values of ampere-turns well above normal operating values. By proper proportioning of the magnetic plate 11 the range may extend to current values causing a destruction of the coil, so that switch closure is definitely precluded. As a consequence an unwanted closing of the contact ends 6, 7 will not occur upon energization of but a single coil 12, or 15, and fluctuations in operating voltage will not alter this switching characteristic. The plate 11 influences the pattern of the magnetic field in the vicinity of the contact ends 6, 7 to maintain a low value to flux density between the reed ends 6, 7 that is insufiicient to develop a closing force between the reeds.

For the condition of a single energized coil, for example coil 12, a substantial amount of the magnetic flux in the right hand end of the associated reed 2 will be shunted elf toward the plate 11 to inhibit the passage of any critically sufficient amount of flux from reed end 6 to reed end 7 that would close the contacts. Flux shunted to, or diverted by, the plate 11 will pass from the plate 11 about the outside of the coil 12 to link therewith, and since it is primarily an air fiux that does not give rise to a closing force for the contact ends 6, 7 it can be termed a leakage fiuX.

The coils 12 and 15 are connected to have their respective magnetic flux components in the reeds 2, 3 add to one another. Thus, for conventional symbolic representation applied to FIG. 1, when a positive voltage signal is simultaneously applied to the terminals 14 and 16 the magnetic flux through the center of each coil 12, 15 will be from the right to the left, and the cumulative effects at the reed contacts 6, 7 will produce a sufiicient magnetic intensity across the open contact gap to move the contact ends into closed position. Thus, switch closure is only established by simultaneous coil energization, and by virtue of the flux diverting plate 11, the unique switch characteristic shown in FIG. 2 is obtained.

' In FIG. 2 the abscissa of the graph represents ampereturns for the coil 12 and the ordinate represents ampereturns for the coil 15. The curve 17 is a plot of limiting values of ampere-turns for the two coils 12, 15 for which switch closure is obtained, and this curve is substantially asymptotic so that there is some threshold value of ampere-turns for each coil that is required for switch closure, even though a very high value of ampere-turns is applied through the other coil. This threshold value is represented by the letter m in FIG. 2. It the two coils 12, 15 are operated with equal ampere-turns switch operation will be along the line 18, and the point 19is the minimum value of equal ampere-turns at which switch closure occurs. It is advantageous to have a locus for the point 19 that requires only small ampere-turn values for the two coils, and by proper dimensioning of the diverter plate 11 and positioning of the coils 12, 15 the coordinates x and y for the point 19 can each be brought within two times the necessary minimum ampere-turns m required for either coil for switch closure.

Referring now to FIG. 3, there is shown a reed relay comprised of a glass envelope 1 and reeds 2 and 3. (Like reference numerals have been applied to parts like those shown in FIG. 1.) Associated with this relay is a magnetic flux diverting plate 11 and a group of operating coils which differ from those in FIG. 1 by the inclusion of supplementary coils that are connected to have reverse turns for establishing magnetic flux components in opposition to that of the main coils. Thus, there is a first coil set comprising a main operating coil 21 encircling the left hand side of the envelope 1 and a supplementary coil 22 on the opposite side of the diverting plate 11 that encircles the right hand side of the envelope 1. One end of the main coil 21 is connected to a common terminal 23, shown as a negative terminal, and the opposite end of the main coil 21 is connected through a lead 24 to the supplementary coil 22 in a manner to have the respective coil windings in opposition to one another..'

The supplementary coil 22 has fewer turns than the main coil 21, and upon energization the magnetic fields due to the common current flowing in the two coil sections 21, 22 will be in opposition to one another, with the field of the larger coil 21 being the larger. But, similarly as for the device of FIG. 1, the reed switch will remain open even though large currents be caused to flow through the first coil set, so that a characteristic curve is obtained which is similar to that in FIG. 2.

A second coil set comprises a main operating coil 25 encircling the right hand side of the envelope 1 and a second supplementary coil 26 on the opposite side of the magnetic plate 11. A lead 27 extends from one end of the coil 25 to a common connection with the coil 21, and another lead 28 joins the opposite end of the coil 25 with the supplementary coil 26. The winding relation between the second main coil 25 and the second supplementary coil 26 is like that of the first coils 21, 22, in

that the turns of the supplementary coil 26 are of lesser.

number and in opposition to the turns of the main coil 25.

The coils are further arranged so that the main coils 21,

25 have their fields add to one another.

In operating the reed switch of FIG. 3 both the first and second set of coils must be operated to close the reed plementary coil 22 will oppose that of the coil 21, andv the reeds 2 and 3 will retain their normally open position, even upon applying excessive overload voltage values. This retention of open contact position results from the presence of the magnetic plate 11, and as in FIG. 1 the pattern of the magnetic field in the vicinity of the reed contact ends is modified by the presence of the surrounding magnetic plate 11 to prohibit the value for the magnetic flux between reeds 2 and 3 from developing a force between the reeds sufiicient to close the switch.

Upon energizing the second coil set, the reeds 2, 3 will close. The magnetic flux of the second main coil 25 established in the right hand reed 3 is cumulative to thatof the first main coil 21, so that for the flux path extending from reed 2 to reed 3, the magnetic intensity between reeds 2, 3 is sharply increased and an attractive force,

sufiicient to close the reed contact ends 6, 7 is attained.

Now, upon deenergizing either the first or second coil set the reed switch will open. The reversed supplementary coil which remains energized, such as the coil .22 in the event the second set of coils 25, 26 are deenergized, will cause a greater reduction in the magnetic forces between the closed relay contacts to ensure an opening action. Thus, the embodiment of FIG. 3 is preferred for applications of an and circuit element in which opening of the switch must occur upon deenergizing only one coil set since it has a greater reliability of operation.

An example of the use of several reed switches with one flux diverting magnetic plate is shown in FIG. 4. A mounting block 30 which may also serve as a terminal block, supports a pair of nonmagnetic shafts 31 and 32. The shafts 31, 32 are each threaded at one end to support a magnetic plate 33, which functions as the plate 11 of FIGS. 1 and 3. A group of three glass enveloped reed switches are inserted in appropriate openings in the magnetic plate 33, and parts of the middle assemblyare broken away to show one of these switches 34. Coil assemblies 35 and 36 are placed over the reed switch 34, one on each side of the plate 33. The particular coil assemblies 35 and 36 have coil sets, similarly as in FIG. 3, and for the coil assembly 35 a main operating winding 37 of one coil set is shown wound about a smaller supplementary winding 38 of the other coil set. These coils are on a bobbin 39 that has one end abutting the plate 33, and its opposite end encircled by a non-magnetic assembly plate 40 that is drawn inwardly against the bobbin 39 by a non-magnetic assembly bolt 41. The bolt 41 extends through the plate 33 to a threaded engagement with a second non-magnetic assembly plate 42 which secures the coil assembly 36 in place. The assembly plates 40, 42 also retain a second set of bobbin assemblies 43, 44 that are associated with and encircle an upper reed switch (not shown).

In some installations it may be desirable to extend the ferro-magnetic path of the magnetic plate 11, or 33, around the outer sides of the coil assemblies, and such an arrangement is shown in the lower part of FIG. 4 for the lowermost reed switch (not shown) that is encircled by a pair of coil assemblies 45 and 46. A pair of magnectic tie rods 47 and 48 which pass through the magnetic plate 43 extend alongside the coil assemblies 45, 46. These rods 47, 48 tie together magnetic end plates 49 and 50, which encircle the outer ends of the coil assemblies 45, 46, and they are also encircled by magnetic tubes 51-54 which areheld in tight abutting relation With the plates 49, 50 and the plate 33. Thus, the plates 49, 50 and the tubes 51-54, together with the rods 47, 48 form magnetic circuits that extend from the flux diverting plate 33 around the outside of the operating coils to provide flux return paths bridging the ends of the individual reeds. In this modification stray air flux is greatly reduced so that magnetic interference between adjacent switches is correspondingly minimized. Compact assemblies can then be made without endangering reliability of performance.

When flux is established in a reed by an associated operating coil encircling such reed, the flux that leaks off the reed from near or at the contact end of the reed must extend back, around the coil to the opposite end of the reed. The plate 11 forms a segment of a path for this flux, which flux would otherwise be solely air flux. The low reluctance of the plate 11 modifies the pattern of the return flux by diverting substantial flux to the plate 11, and this flux diverting property of the plate 11 functions to affect the leakage flux leaving the reed. The effect upon the leakage field, then, is to reduce the working flux between the reed contact ends when one coil is energized, to thereby preclude switch closure.

The plate 11 must be of sufiicient thickness, and the opening 10 must have small enough diameter, to divert enough leakage flux to sufiiciently reduce the net closing arrangements of FIGS. 1 and 3.

flux diverting member should be at least as great as the overlap of the reed contact ends.

It is desirable to proportion each operating coil to develop a magnetizing force that substantially saturates the associated reed when drawing rated current, and economical use of both the coil and reed materials may then be achieved. The reeds may also be designed to magnetically saturate with a small increase of ampere-turns over that which is sufiicient for closure. Then, increased excitation of the coil will not produce large increments of flux at the reed contact ends, so the flux diverting plate is not called upon to handle excessive amounts of flux under overload conditions of the coil and the flux through the contact ends to cause contact closure will not increase markedly.

For the device of FIG. 3 the smaller supplementary coils may be placed inside the main coils, as shown for coils 37 and 38 in FIG. 4, or they may be placed toward the center of the envelope 1, as schematically indicated in FIG. 3. Their modifications of the magnetic field may then affect switch operation while remaining at a number of turns substantially less than the number of main coil turns. For the concentric arrangement of FIG. 4 a ratio of from two to one to four to one for the main coil turns to the supplementary coil turns has been found satisfactory for usual operation, and the axially inner ends of the coils should be set back from the flux diver-ting plate for about inch for a reed switch of the above discussed dimensions.

In summary, the invention provides a reed switch control, in which two signals are required for initial switch operation, making novel use of a flux diverting member positioned at the reed contacts to modify the magnetic field, and this in turn provides for elimination of critical operating limitations. Further, supplementary coils can be employed to insure proper opening action for an and logic circuit element.

I claim:

1. In a control for a reed switch having a pair of elongated, electrically conductive magnetic reeds which have relatively movable, facing, normally open contact ends, the combination comprising: a flux diverting member of a magnetic material disposed closely adjacent to the reed contact ends that provides a region of low reluctance restricted to the vicinity of the reed contact ends; a pair of operating coil sets, each of said sets including a main coil magnetically encircling one of said reeds to directly establish magnetic flux in the reed which is disposed on one side of the flux diverting member and a supplementary coil magnetically I encircling the other reed to directly establish magnetic fiux in the reed that is disposed on the opposite side of the flux diverting member and adapted to establish in its associated reed magnetic flux opposite in direction and of less magnitude than the magnetic flux established by the main coil, the main coils of the coil sets being on opposite sides of the flux diverting member and being adapted to establish magnetic flux through the reeds in the samedirection, said reeds comprising substantially the only magnetic flux path of magnetic material within the center of the coils of each coil set, and said flux diverting member conducting flux from the reed contact ends for leading flux from the contact ends in a path around the outer sides of the coils, such that upon energization of a single coil set the flux conduction of the flux diverting member and the opposing flux of the sup plementary coil preclude closure of the reeds whereby energization of both coil sets is required for reed closure, continued energization of both coil sets is required for maintaining reed closure, and upon de-energization of either coil set the flux conduction of the flux diverting member and the opposing flux of the supplementary coil that is still energized causes positive opening of said reeds.

2. The reed switch control of claim 1 characterized in that the ratio of turns between each main coil and its supplementary coil is of the order of 2:1 to 4:1.

3. In a reed switch control including a reed switch hav ing an enclosing envelope and a pair of magnetic, electrically conductive reeds therein which have relatively mov. able contact ends facing one another in overlapping relation to form switch contacts the combination comprising: a magnetic member closely encircling the movable contact ends of said reeds that provides a flux return path from either reed contact end to the opposite end of the same reed that includes a-portion of the magnetic member and which is of lower reluctance than a path extending from the reed to the other reed and then to the opposite end of the first reed, said magnetic member being restricted in its longitudinal extent along said enclosing envelope to the vicinity of the reed contact ends, but being of a thickness at least as great as the overlap of said reed contact ends and being centered therewith; a first coil set comprising a first main coil section magnetically encircling one reed of the switch to directly establish magnetic flux in the reed and a first supplementary coil ,sec-

tion on the'o'pposite side of said magnetic member tnag-' netically encircling the other reed to directly establish magnetic flux therein which is connected with respect to' stantially the only magnetic flux paths of magnetic ma-' terial within the centers of all of said main and supplementary coil sections, and said supplementary coil sections each being of lesser turns than the associated main coil section, whereby initial closure and maintenance of closure of said switch contacts requires concurrent energization of both of said coil sets.

References Cited by the Examiner UNITED STATES PATENTS 7 3,059,075 10/1962 Peek ZOO-87 3,075,059 1/1963 Blaha et a1. 200-87 3,141,079 7/1964 Lowry 200-87 3,182,226 5/1965 Peek 200-87 BERNARD A. GILHEANY, Primary Examiner.

B. DOBECK, Assistant Examiner. 

1. IN A CONTROL FOR A REED SWITCH HAVING A PAIR OF ELONGATED, ELECTRICALLY CONDUCTIVE MAGNETIC REEDS WHICH HAVE RELATIVELY MOVABLE, FACING, NORMALLY OPEN CONTACT ENDS, THE COMBINATION COMPRISING: A FLUX DIVERTING MEMBER OF A MAGNETIC MATERIAL DISPOSED CLOSELY ADJACENT TO THE REED CONTACT ENDS THAT PROVIDES A REGION OF LOW RELUCTANCE RESTRICTED TO THE VICINITY OF THE REED CONTACT ENDS; A PAIR OF OPERATING COIL SETS, EACH OF SAID SETS INCLUDING A MAIN COIL MAGNETICALLY ENCIRCLING ONE OF SAID REEDS TO DIRECTLY ESTABLISH MAGNETIC FLUX IN THE REED WHICH IS DISPOSED ON ONE SIDE OF THE FLUX DIVERTING MEMBER AND A SUPPLEMENTARY COIL MAGNETICALLY ENCIRCLING THE OTHER REED TO DIRECTLY ESTABLISH MAGNETIC FLUX IN THE REED THAT IS DISPOSED ON THE OPPOSITE SIDE OF THE FLUX DIVERTING MEMBER AND OPPOSITE TO ESTABLISH IN ITS ASSOCIATED REED MAGNETIC FLUX OPPOSITE IN DIRECTION AND OF LESS MAGNITUDE THAN THE MAGNETIC FLUX ESTABLISHED BY THE MAIN COIL, THE MAIN COILS OF THE COIL SETS BEING ON OPPOSITE SIDES OF THE FLUX DIVERTING MEMBER AND BEING ADAPTED TO ESTABLISH MAGNETIC FLUX THROUGH THE REEDS IN THE SAME DIRECTION, SAID REEDS COMPRISING SUBSTANTIALLY THE ONLY MAGNETIC FLUX PATH OF MAGNETIC MATERIAL WITHIN THE CENTER OF THE COILS OF EACH COIL SET, AND SAID FLUX DIVERTING MEMBER CONDUCTING FLUX FROM THE REED CONTACT ENDS FOR LEADING FLUX FROM THE CONTACT ENDS IN A PATH AROUND THE OUTER SIDES OF THE COILS, SUCH THAT UPON ENERGIZATION OF A SINGLE COIL SET THE FLUX CONDUCTION OF THE FLUX DIVERTING MEMBER AND THE OPPOSING FLUX OF THE SUPPLEMENTARY COIL PRECLUDE CLOSURE OF THE REEDS WHEREBY ENERGIZATION OF BOTH COIL SETS IS REQUIRED FOR REED CLOSURE, CONTINUED ENERGIZATION OF BOTH COIL SETS IS REQUIRED FOR MAINTAINING REED CLOSURE, AND UPON DE-ENERGIZATION OF EITHER COIL SET THE FLUX CONDUCTION OF THE FLUX DIVERTING MEMBER AND THE OPPOSING FLUX OF THE SUPPLEMENTARY COIL THAT IS STILL ENERGIZED CAUSES POSITIVE OPENING OF SAID REEDS. 